Electronic and optoelectronic component packaging technique

ABSTRACT

A packaging method including assembling components on a substrate, manufacturing a lid assembly to include a plurality of integrated covers, and mating the lid assembly to the substrate.

RELATED APPLICATIONS

This application is a divisional of prior application Ser. No.10/460,852 filed Jun. 13, 2003, now U.S. Pat. No. 6,952,046 which claimsbenefit of and priority to provisional application Ser. No. 60/390,011filed Jun. 19, 2002.

GOVERNMENT RIGHTS

This invention was made with U.S. Government support under Contract No.DAAH01-00-C-R070 awarded by the U.S. Army. The Government may havecertain rights in the subject invention.

FIELD OF THE INVENTION

This invention relates to an electronic and optoelectronic componentpackage, a unique lid assembly, and several useful package sealingtechniques.

BACKGROUND OF THE INVENTION

Semi-conductor packaging is an active field. U.S. Pat. No. 5,827,999,incorporated herein by this reference, delineates the limitationsassociated with numerous prior art packaging techniques includingencasement, the cavity package, and various thermoplastic chip carrierpackages. The basic purpose of any semi-conductor package is protectionof the component(s) (e.g., electronic chips, electrooptical devices, andthe like) housed by the package while at the same time providingelectrical and/or optical interconnections from the component(s) throughthe package. Manufacturability and protection are key concerns. Theapplicant owns U.S. Pat. No. 6,320,257 disclosing a semiconductorpackaging technique comprising an interconnect substrate including atleast one layer of LCP material, at least one semiconductor componentbonded to the substrate, a lid, and a hermetic seal sealing the lid tothe substrate. This patent is hereby incorporated herein by thisreference. The '999 patent discloses the idea of molding a casing ontothe circuit substrate around a chip. The casing can be made of, amongother things, liquid crystal polymer material. As recognized by theinventors hereof, LCP materials have a very low moisture permeabilityand can provide a hermetic seal especially if the package lid coveringthe chip and also the substrate which supports the chip are both made ofLCP or even if the lid assembly is composed of a metal, ceramic, orglass. Other relevant art includes U.S. Pat. Nos. 6,403,211; 6,538,211;6,057,597; 6,428,650; 6,136,128; 5,761,053; 6,501,654; and 5,471,011;and Patent Publication Nos. US 2003/0002265; US 2002/0187570; US2001/0019475; US 2003/0026556; US 2003/0044130; US 2002/0197026; US2003/0057535; and US 2003/0045024.

This art, however, is not primarily concerned with manufacturability. Inmost, if not all cases, a single component is mounted to a circuitsubstrate and then the lid or cover is secured over the component to thesubstrate. Assembly of the components as single entities consumesunnecessary time, effort, and cost in the component assembly process.Also, the art listed above is not primarily concerned with feasibilitystudies to ascertain the most economical methods of sealing the coverover the component to the substrate.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a highlyefficient package lid and substrate assembly process.

It is a further object of this invention to provide such a process whichresults in precision alignment of the package lids to the interconnectsubstrate.

It is a further object of this invention to provide such a process whichis versatile and can accommodate many different types of components,substrate designs, cover designs, and sealing processes.

It is a further object of this invention to provide a novelsemi-conductor package lid sub-assembly.

It is a further object of this invention to provide new ways ofefficiently and effectively sealing the cover over the component(s) tothe substrate.

This invention results from the realization that a highly effectivepackage lid and assembly process is effected by injection molding anumber of individual covers as an integrated lid sub-assembly, mating apopulated interconnect substrate with the integrated lid sub-assembly,and then singulating the individual packages. Sealing the individualcovers over a component to the substrate can be accomplished beforesingulation or even after singulation using a variety of differentefficient methods.

This invention features a package comprising a substrate, a plurality ofcomponents on the substrate, and a lid assembly including a plurality ofintegrated covers for at least select components on the substrate.

In one example, the lid assembly includes a plurality of integralalignment pins and the substrate includes alignment holes which receivethe alignment pins to position the covers with respect to thecomponents. Typically, the pins are made of meltable material and thecovers are spaced from each other and the alignment pins are positionedin the spaces between the covers.

In one embodiment, the substrate is formed of at least one layer of aliquid crystal polymer material. The liquid crystal polymer material maybe bi-axially oriented. In one example, the substrate is a printedcircuit board and there is a cover for each component on the substrate.Then, the covers are formed in an array and extend outward from aninterconnecting layer. Preferably, the lid assembly is formed of aliquid crystal polymer material.

Also, there is a seal between each cover and the substrate such as alaser welded seal, or an ultrasonically created seal. A susceptormaterial may be placed between the covers and the substrate to absorblaser energy when the covers are laser welded to the substrate. Thesubstrate may include pigmentation to absorb laser energy when thecovers are laser welded to the substrate or the covers may includepigmentation to absorb laser energy when the covers are laser welded tothe substrate. The covers may include energy directors for focusingultrasonic energy when the covers are ultrasonically welded to thesubstrate. In one example, the substrate includes cavities formedtherein which received the energy directors of the covers.

Typically, each cover includes sidewalls and a cap. There may be foursidewalls. Also, the lid assembly may further include a layerinterconnecting the caps of each cover which can be removed to singulatethe individual covers. In one embodiment, the cap includes an opticalwindow sealed to the cap by a laser. Preferably, the sidewalls include alower lip. And, in one example, each cover includes sidewalls eachterminating in a lip, the lips co-joined by an interconnecting layer.

This invention also features a packaging method comprising assemblingcomponents on a substrate, manufacturing a lid assembly to include aplurality of integrated covers, and mating the lid assembly to thesubstrate.

In one embodiment, the substrate includes alignment holes andmanufacturing includes forming alignment pins extending from the lidassembly which are received in the alignment holes of the substrate toposition the lid assembly covers with respect to the components. Furtherincluded may be the step of melting the pins to secure the lid assemblyto the substrate. Typically, the individual covers are singulated.Manufacturing may include forming a layer interconnecting the covers andsingulation includes removing the interconnecting layer. Or,manufacturing may include forming a layer interconnecting the covers andsingulation includes cutting through the interconnecting layer betweenthe individual covers. Cutting further may further include cutting thesubstrate between the individual covers.

In one example, manufacturing includes injection molding spaced coversto each include sidewalls and a cap, the caps of all the coversinterconnected by an interconnecting layer. Mating may include adding abonding agent between the end of each cover sidewall and the substrate.Typically, the substrate is formed of at least one layer of a liquidcrystal polymer material. In one example, the liquid crystal polymermaterial is bi-axially oriented. In one embodiment, the substrate is aprinted circuit board and there is a cover for each component on thesubstrate. In one example, the covers are formed in an array and extendoutward from an interconnecting layer. Further included may be the stepof sealing each cover with respect to the substrate. Sealing includeslaser welding. A susceptor material may be disposed between the coversand the substrate to absorb laser energy when the covers are laserwelded to the substrate. Also, pigmentation can be added to thesubstrate to absorb laser energy. Or, pigmentation can be added to thecovers to absorb laser energy. In another example, sealing includesultrasonically welding each cover to the substrate. In this example,energy directors may be formed in the covers for focusing the ultrasonicenergy and cavities may be formed in the substrate to receive the energydirectors. Typically, a lower lip is formed for each cover. In oneembodiment, the lips of all covers are co-joined by an interconnectinglayer.

A lid assembly in accordance with this invention includes a plurality ofcovers each including sidewalls and a cap and an interconnecting layerwhich integrates the covers for placement in unison over components on asubstrate. Typically, the covers and the interconnecting layer areformed of a liquid crystal polymer material by injection molding. In oneexample, the interconnecting layer is a continuous layer spanning thecaps of all the covers. In another example, the sidewalls include alower lip portion and the interconnecting layer co-joins the lower lipportions of the covers.

One package in accordance with this invention includes a substrate madeof LCP material, a plurality of components on the substrate, and a lidassembly including a plurality of integrated covers all made of LCPmaterial and secured to the substrate, each cover disposed over acomponent.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages will occur to those skilled inthe art from the following description of a preferred embodiment and theaccompanying drawings, in which:

FIGS. 1A-1D are schematic three-dimensional views showing variousconventional package designs useful in connection with optoelectriccomponents;

FIG. 2 is a schematic three-dimensional bottom view showing, in oneexample, a lid sub-assembly in accordance with the subject invention;

FIG. 3 is a schematic three-dimensional view showing a printed circuitboard substrate before it is populated with components;

FIG. 4 is a schematic three-dimensional partial cross-sectional view ofthe lid sub-assembly shown in FIG. 1;

FIG. 5 is a schematic three-dimensional view showing the printed circuitboard substrate of FIG. 2 now populated with components;

FIG. 6 is another schematic three-dimensional view showing one exampleof a lid sub-assembly in accordance with the subject invention;

FIG. 7 is a schematic three-dimensional view of the lid sub-assembly ofFIG. 6 with a susceptor compound now in place on the bottoms of theindividual covers;

FIG. 8 is a schematic three-dimensional view showing the lidsub-assembly of FIG. 7 being mated to the populated circuit boardsubstrate using the alignment pins of the subject invention;

FIG. 9 is a schematic three-dimensional view showing how, in oneembodiment, the alignment pins of the lid sub-assembly are melted to thesubstrate to secure the lid subassembly in place on the substrate;

FIG. 10 is a schematic three-dimensional view showing the lidsub-assembly now mated to the substrate in accordance with the subjectinvention just before singulation;

FIG. 11 is a schematic three-dimensional view showing the individualcovers after singulation in accordance with one embodiment of thesubject invention;

FIG. 12 is a schematic three-dimensional view showing singulation of thecovers and the substrate at the same time in accordance with the anotherembodiment of the subject invention;

FIG. 13 is a schematic three-dimensional view showing another type oflid sub-assembly interconnection layer in accordance with the subjectinvention;

FIG. 14 is a schematic three-dimensional view showing another type ofcover in accordance with the subject invention including an opticalwindow;

FIG. 15 is a schematic cross-sectional view of the optical window typecover of FIG. 14;

FIG. 16 is a schematic view showing an array of covers each including alower lip portion in accordance with the subject invention;

FIG. 17 is a schematic view showing a single cover of the array ofcovers shown in FIG. 16 just before it is sealed over a component andonto the substrate;

FIG. 18 is a schematic partial cross-sectional view showing how thelower lip assembly of a single cover is sealed with respect to thesubstrate in accordance with one embodiment of the subject invention;

FIG. 19 is a schematic partial cross-sectional view showing anothermethod of sealing a cover to a substrate;

FIG. 20 is a schematic partial cross-sectional view showing stillanother method of sealing a cover to a substrate;

FIG. 21 is a schematic partial cross-sectional view showing stillanother method of sealing a cover to a substrate in accordance with thesubject invention;

FIG. 22 is a schematic view showing a frame-shaped ultrasonic hornuseful in connection with the subject invention for ultrasonicallysealing a cover to a substrate;

FIG. 23 is a bottom view of a single cover including a metallizationlayer in accordance with one embodiment of the subject invention;

FIGS. 24-29 are schematic views showing the steps involved in packagingelectronic components in accordance with this invention and also showinganother embodiment of the lid assembly in accordance with thisinvention; and

FIG. 30 is a schematic view showing still another lid assemblyembodiment in accordance with the invention.

DISCLOSURE OF THE PREFERRED EMBODIMENT

Aside from the preferred embodiment or embodiments disclosed below, thisinvention is capable of other embodiments and of being practiced orbeing carried out in various ways. Thus, it is to be understood that theinvention is not limited in its application to the details ofconstruction and the arrangements of components set forth in thefollowing description or illustrated in the drawings.

FIGS. 1A-1D show typical packages 5A-5D for optoelectronic components.One goal of the subject invention is to provide packages foroptoelectronic and other components which are more efficientlymanufactured and assembled thus reducing costs.

FIG. 2 shows, in one example of the subject invention, lid assembly 10which includes an array of individual covers 12 each cover including,typically, four side walls 14 and a covering cap or top 15 (see FIG. 4).Interconnecting layer 16, FIGS. 1 and 4, in this embodiment, acontinuous plate which integrates covers 12 for placement in unison overmultiple components on a substrate.

Lid assembly 10 is typically molded from filled LCP material (e.g., 30%glass filler) and may even include multi-axially oriented material asdiscussed in the applicant's U.S. Pat. No. 6,320,257 herein incorporatedby this reference. The use of LCP in place of other thermoplasticpolymers is preferred because LCP exhibits superior barrier properties,high use temperature, and dimensional stability for precision moldingtolerances. Other thermoplastics, other materials, and other formingprocesses, however, may also be used.

In one preferred embodiment, alignment pins 18, also made of LCPmaterial, extend outward from the molded interconnecting layer 16 in thespaces between the covers. Then, chip circuit board substrate 20, FIG. 3includes corresponding alignment holes 22. Substrate 20 typicallyincludes at least one layer, preferably the top layer, of multi-axiallyoriented LCP material as set forth in U.S. Pat. No. 6,320,257 (see FIGS.2b and 3 thereof). Thus, substrate 20, typically a printed circuitboard, can accommodate a wide variety of different types of components(chips, optical devices, MEMs devices, and the like) and alsoaccommodates a number of different chip mounting technologies (wirebonding, ball grid arrays, surface mount technology, and the like).Areas 24 on substrate 20 are dedicated to the components 26 as shown inFIG. 5.

In one example, a bonding agent, an adhesive, and/or a susceptor (e.g.,Clearweld™) material 30, FIG. 2 may be dispensed (e.g., screened) ontothe distal end of each sidewall, or onto the mating surface on thesubstrate, before lid assembly 10 is mated to the populated substrate20, FIG. 8 as the alignment pins 18 are received in the alignment holesas shown at 32. Next, ultrasonic horn 40, FIG. 9 can be used to melt thedistal ends of the alignment pins to secure lid assembly 10 to substrate20. Melting/welding of the alignment pins is not a necessary step as thesubsequent lid sealing process can form a sufficient mechanical bond ofthe lid to the substrate. Each cover may also be hermetically sealed tosubstrate 20 at this stage in the assembly process using one or more ofthe techniques discussed below. Each cover is typically associated withone component but a cover may also be disposed over multiple components.

Singulation can be carried out in a number of different ways. In FIG.10, integration layer 16 is removed by back lapping, for example, toseparate each cover 12, FIG. 11. Then, substrate 20 is singulated in oneprocess step using conventional techniques. Or, in other embodiments,substrate 20 may be left intact.

Alternatively, singulation of both the covers and substrate 20, FIG. 12can be accomplished by cutting through both integration layer 16 andsubstrate 20 as shown in FIG. 12 along lines 50 using (a routing tool,laser, water jet, or other cutting apparatus). If the lid assembly andthe substrate are manufactured in a certain way, the modules may besnapped apart rather than cut apart. For vibration or shock sensitivecomponents this may not be feasible, but in some cases asnap-singulation may be practical. The substrate would have to beembossed, etched, or scribed to snap along a line and the mating lidassemble would also have to include a snap line.

FIG. 13 shows a different kind of interconnecting layer 16 a spanningthe tops 15 of each cover 12. The interconnection part of the lidsdepicted in FIG. 13 may be the runners used to injection mold the lidassembly. Again, this whole package lid sub-assembly can be molded inthe form shown in FIG. 13. Covers 12 are singulated by removing layer 16a and/or cutting through it in the areas between the individual covers.

FIGS. 14-15 show a different type of cover 12 a including optical window60 useful when the component housed in cover 12 a is an optical device.Walls 14 a of cover 12 a include ledge 62 which supports optical window60. Window 60 may be laser welded in place on ledges 62. The opticalwindow 60 may be made of a number of optical materials formed into anumber of shapes (e.g., flat optical window, collimating lens,micro-lens arrays, and the like).

FIG. 16 shows alternative covers 12 b extending outward from integrationlayer 16 each including lower lip 70 useful, as described below, forsecuring the covers to a substrate using a variety of different sealingprocesses in accordance with the subject invention and interconnected bya bulk of injection molded material. This formation of the lid assemblycan be locked in place or sealed and then backlapped to singulate thelids.

The subject invention also includes a wide variety of methods forhermetically sealing lip 70, FIG. 17 of cover 12 over component 24 onsubstrate 20 either after cover 12 is singulated as shown in FIG. 17 oreven before cover 12 is singulated (i.e. when cover 12 is stillinterconnected to a number of similarly constructed covers). Typically,cover 12 is injection molded out of a filled LCP material and substrate20 is made of or includes bi-axially oriented LCP material.

LCP material is somewhat transparent to near-infrared radiation. Thus,in one example, susceptor material 100, FIG. 18 (e.g., Clearweld™, or analternative IR absorbing material) is placed between lower lip 70 of thecover and substrate 20 and infrared laser energy 102 is used to heat theinterface between cover lip 70 and substrate 20 as the laser energy isabsorbed by susceptor material 100. The result is localized heatingwhich melts and seals the LCP material at the interface between lip 70and substrate 20. The susceptor material may be printed, jetted,screened, or painted onto the lower lip of the cover and/or onto thesubstrate or even plated thereto. The thickness of lip 70 should be nogreater than 32 mils to achieve proper heating and a hermetic seal.

In another example, the LCP material of at least the top layer ofsubstrate 20′, FIG. 19 is pigmented with, for example, carbon resin 110prior to injection molding or extrusion of the material. When laserenergy 102 hits the pigmented substrate after passing through lip 70,heat is generated at the contact point between lip 70 and substrate 20′and a hermetic seal is created. The thickness, width, and geometry oflower lip 70 all play a part in the sealing effectiveness and can beoptimized for various different designs.

Another option is to pigment at least lip portion 70′, FIG. 20 of thecover and direct laser energy 102 to lip portion 70′ through substrate20. Now, the thickness of substrate 20 should be in the 2 to 20 milrange. Pigmentation of the substrate (FIG. 19) or cover (FIG. 20) can beaugmented with susceptor layer 100, FIG. 18. Standard diode laserwelding systems can be used as the source of laser energy.

In still another example, lower lip 70′, FIG. 21 of the cover includesenergy directing prongs 120 which are received in cavities 122 formed insubstrate 20′. An ultrasonic horn 140 is used to create heat at theinterface between lower lip 70′ and substrate 20′. Energy directors 120are integrated into the lid design to focus the ultrasonic energy inorder to induce melting at the interface and provide a hermetic seal.

In FIG. 22 a plunge welding type ultrasonic welding system is used withframe shaped horn 142 which engages all four sides of lower lip 70 ofthe cover simultaneously to hermetically seal cover 12 to substrate 20in a single operation.

Finally, soldering as a sealing method can be used if LCP lip 70″ or theentire cover, FIG. 23 is metallized on the bottom thereof at sealinginterface 150 and if the substrate, not shown, also includesmetallization which mates with the lip of the cover.

The result is a hermetically sealed package and an efficient, scalableassembly process reducing time, effort, and cost. Depending on the sizeof the component(s), panel level assembly as described herein canincrease the manufacturing efficiency by an estimated 50% or more.Typically, the package lid assembly is manufactured by injectionmolding. The printed circuit board may be manufactured with a footprintfor package sealing and precision alignment holes for aligned mating.The board is populated with the various components which may beelectrical, optoelectronic, and the like and then the panel of packagelids is mated with the component substrate. The panel lid assembly islocked to the substrate to maintain alignment and then each cover issealed before or after singulation of the packages. The alignment andlocking method described above is one of many possible mechanisms.Alternatives include, but are not limited to, alignment fiducials formedout of etched metal, screened on chemistries, drilled, and depositedmetal. These alignment fiducials will be located on both the substrateand the mating lid. As for the alignment pins, in addition to a straightpin that is ultrasonically melted to secure the assembly, a snap-fitalignment pin may also be implemented. The preferred substrate iscomposed of at least one layer of biaxially or multiaxially oriented LCPfilm and bond areas for silicon dice, integrated circuits, MEMs, MOEMs,or a variety of electronic or optoelectronic components that requirepackaging. One advantage of the subject invention is passive alignmentvia the alignment holes and the alignment pins. The dimensionalstability of the package lids and the dimensional stability the circuitboard are tight enough to eliminate the need for special alignmentmethods for panel level assembly. Passive alignment is especiallyimportant in the optoelectronic component arena, but may be useful formultimode applications where the tolerances are on the order of microns,rather than nanometers (singlemode fibers). When a component includes aglass window, a lens array, or other optical devices that requirealigned mating, passive alignment within a few microns is achieved andthe subject invention saves significant manufacturing time and money.

FIGS. 24-29 illustrate one possible packaging technique in accordancewith the subject invention. LCP substrate 200 FIG. 24 is biaxial ormultiaxial or includes layers of uniaxial LCP cross-plied. Alignmentholes 202 are formed in at least the top layer of substrate 200. Areas204 receive the various components. Molded LCP assembly 208, FIG. 25includes integrated covers 210 and alignment pins 212. This embodiment,each cover includes sidewalls 209 terminating in lip 213. The lips ofall covers are co-joined by interconnecting layer 215. After substrate200 is populated with components 211 as shown in FIG. 26, lid assembly208, FIG. 27 is mated with substrate 200 as alignment pins 212 arereceived in alignment holes 202. Laser 218, FIG. 28 is the used to sealall individual covers 210 to substrate 200. Singulate is theaccomplished as shown in FIG. 24 using router 220. The result isindividual packages as discussed above.

FIG. 30 shows another embodiment of an array of LCP covers 250interconnected by runners 252 which, during singulation, can be brokenor cut.

Although specific features of the invention are shown in some drawingsand not in others, this is for convenience only as each feature may becombined with any or all of the other features in accordance with theinvention. The words “including”, “comprising”, “having”, and “with” asused herein are to be interpreted broadly and comprehensively and arenot limited to any physical interconnection. Moreover, any embodimentsdisclosed in the subject application are not to be taken as the onlypossible embodiments. Other embodiments will occur to those skilled inthe art and are within the following claims.

1. A packaging method comprising: assembling components on a substrate,the substrate including alignment holes; manufacturing a lid assembly toinclude a plurality of integrated spaced individual covers eachincluding sidewalls and a cap, said manufacturing further including:forming a layer interconnecting the caps of the covers, each of theindividual covers extending outward from the interconnecting layer, andforming alignment pins extending from the lid assembly which arereceived in the alignment holes of the substrate to position the lidassembly covers with respect to the components; and mating the lidassembly to the substrate.
 2. The method of claim 1 further includingthe step of melting the pins to secure the lid assembly to thesubstrate.
 3. The method of claim 1 further including the step ofsingulating the individual covers.
 4. The method of claim 3 in whichsingulation includes removing the interconnecting layer.
 5. The methodof claim 3 in which singulation includes cutting through theinterconnecting layer between the individual covers.
 6. The method ofclaim 5 wherein cutting further including cutting the substrate betweenthe individual covers.
 7. The method of claim 1 in which manufacturingincludes injection molding the spaced covers.
 8. The method of claim 1in which mating includes adding a bonding agent between the end of eachcover sidewall and the substrate.
 9. The method of claim 1 in which thesubstrate is formed of at least one layer of a liquid crystal polymermaterial.
 10. The method of claim 9 in which the liquid crystal polymermaterial is bi-axially oriented.
 11. The method of claim 1 in which thesubstrate is a printed circuit board.
 12. The method of claim 1 in whichthere is a cover for each component on the substrate.
 13. The method ofclaim 1 in which the covers are formed in an array.
 14. The method ofclaim 1 further including the step of sealing each cover with respect tothe substrate.
 15. The method of claim 14 in which sealing includeslaser welding.
 16. The method of claim 15 further including the step ofdisposing a susceptor material between the covers and the substrate toabsorb laser energy when the covers are laser welded to the substrate.17. The method of claim 15 further including adding pigmentation to thesubstrate to absorb laser energy.
 18. The method of claim 15 furtherincluding adding pigmentation to the covers to absorb laser energy. 19.The method of claim 14 in which sealing includes ultrasonically weldingeach cover to the substrate.
 20. The method of claim 19 in which energydirectors are formed in the covers for focusing the ultrasonic energy.21. The method of claim 20 in which cavities are formed in the substrateto receive the energy directors.
 22. The method of claim 1 furtherincluding forming a lower lip for each cover.
 23. The method of claim 1in which the lips of all covers are co-joined by an interconnectinglayer.
 24. The method of claim 1 further including forming a window foreach cover.
 25. The method of claim 24 further including sealing thewindow to the cover using a laser.